Conventional multi-needle embroidery sewing machine is capable of consecutive executions of embroidery sewing operations with multiple thread colors. Such multi-needle embroidery sewing machine has a needle-bar case containing six needle bars, for instance, provided at the extremity of its arm. The required needle bar is selected from the needle bars contained in the needle-bar case by moving the needle-bar case in the left and right direction. The selected needle bar is thereafter connected to the needle-bar drive mechanism and driven up and down to execute the sewing operation.
The controller of the sewing machine receives input of pattern data that contains instructions on stitch-by-stitch needle drop point, which determines the movement amount of workpiece cloth, and timing for changing the thread color, etc. Based on the pattern data, the controller transfers the embroidery frame holding the workpiece cloth in the X and Y directions by the transfer mechanism while controlling the needle-bar drive mechanism and other drive mechanisms to form embroidery in multiple colors.
Recent developments in the above described multi-needle embroidery sewing machine is provision of a decoration feature for decorating a cloth using a method called needle punching. To elaborate, some of the needle bars mount a needle punch needle in place of an ordinary sewing needle for needle punching the workpiece cloth based on needle punch information.
A recent example of such feature is realized, for instance, by a puncher applying a dot impact printer that creates accessories and furnishings by punch engraving desired pictures, illustrations, and characters on objects such as plastic or metal plates and wooden or fiber-made boards with a punch needle. The puncher is configured to create a predetermined punch engraving on the surface of the workpiece by transferring the printer head provided with a plurality of punch needles in the X direction while transferring the workpiece in the Y direction.
Such feature of the puncher may be implemented on the above described multi-needle sewing machine by attaching a punch needle on some of the needle bars in place of a sewing needle. In such case, because the punch needle is designed to only impact the surface of the workpiece, it needs to be dimensioned in shorter length as compared to a sewing needle that penetrates the workpiece cloth. Further, a holder for holding the workpiece in place is attached to the carriage of the transfer mechanism instead of an embroidery frame for holding the workpiece cloth. The desired punch engraving can be formed on the surface of the workpiece by moving the workpiece based on punch engraving data and driving the needle bar mounted with the punch needle up and down.
However, mere replacement of sewing needle to punch needle on some of the needle bars of the multi-needle sewing machine is likely to introduce the following inappropriate occurrences. The user may accidentally start the embroidery sewing operation in which the needle bar having the sewing needle attached to it is driven up and down with the holder for punch needle attached to the carriage of the transfer mechanism. In such case, the sewing needle descends further downward as compared to the punch needle and thus, suffers a hard impact with the workpiece to damage itself or the workpiece especially since the workpiece held by the punch workpiece holder is made of relatively hard material.
In contrast, when the needle bar mounted with punch needle is accidentally moved up and down with the embroidery frame holding the workpiece attached to the carriage of the transfer mechanism, the punch needle may damage the workpiece cloth. Another possibility is that punch engraving operation such as the drive of the needle bar mounted with punch needle may be executed unwantedly based on the pattern data intended for embroidery sewing. In such case, needless or inappropriate operations such as thread wiping and thread cutting may be encountered during the punch engraving operation or the needle bar may be driven at excessive speed, for instance, that is unsuitable for punch engraving.